Polyester oligomers and copolymers containing significant quantities of hydrophilic moieties, are generally referred to as "hydrophilic" polyester oligomers or polymers and have been known for some time. They generally contain, sometimes along with other components, segments derived from low molecular weight glycols and segments derived from polyethylene oxides which impart the hydrophilic properties to the oligomer or polymer in which they are incorporated. They may be prepared by condensation, accomplished by heating to relatively high temperatures under relatively high vacuums, mixtures of diesters, simple glycols and polyethylene ether glycols. By-product alcohols and part of the alkylene glycol originally charged, are removed by distillation during the processing. The resulting copolyester probably consists of polyalkylene diester segments and polyoxyethylene diester segments randomly dispersed along the polymeric chain. Typically the copolyesters contain polyethylene terephthalate and polyoxyethylene terephthalate segments because of price and availability of the monomers, and similarity of structure to the high volume polyester fibers.
Copolyesters of the type discussed above, are disclosed in McIntyre et al., in U.S. Pat. Nos. 3,416,952, 3,557,039 and 3,619,269, which also describe the introduction of several other types of components into the polyester for application to fibers and films for enhancement of various properties. Similarly, Raynolds in U.S. Pat. No. 3,981,807, reports a variety of modified copolyesters for application to textiles. Gillberg-LaForce et al., in U.S. Pat. No., 4,569,974, describe hydrophilic copolymers containing polyhydroxy moieties derived from such compounds as pentaerythritol, glycerin and their low molecular weight oligomeric ethers. Gosselink et al., in U.S. Pat. Nos. 4,702,857, 4,711,730 and 4,713,194, disclose hydrophilic copolyesters prepared from diesters, low molecular weight diols and polyalkylene oxides capped at one end with an ether group, for use as soil release agents in detergent compositions. Gosselink also discloses in U.S. Pat. No. 4,721,580, copolyesters derived from diesters, low molecular weight diols and polyalkylene oxides capped at one end with a salt of a sulfonic acid, for the same application. Teijin EP 159882 describes as useful for incorporating polyester fibers into paper-making, hydrophilic copolyesters prepared from diesters of tere- or isophthalic acid, a low molecular weight glycol, a polyethylene glycol and a salt of a sulfonated phthalic acid. ICI Americas EP 66944 describes similar copolymers which may also contain aliphatic diester moieties and which are useful as textile treating agents.